How transgenic and classically bred apple genotypes affect non-target organisms on higher trophic levels

Current plant breeding comprises classical techniques as well as biotechnological methods suitable to insert target genes into the plant genome. Potential non-target effects of these newly developed plants have to be evaluated in appropriate risk assessment studies. We investigated non-target effects of four apple genotypes (Malus × domestica L. Borkh.; Rosaceae). They were either susceptible or resistant to the fungal phytopathogen causing apple scab, Venturia inaequalis (Cke.) Wint. (Ascomycotina: Pleosporales), and were either of transgenic origin or classically bred, differing in or sharing a single trait each. Experiments on insect performance were carried out with two non-target species, namely the apple leafminer Phyllonorycter blancardella Fabricius (Lepidoptera: Gracillariidae) and its parasitoid Pholetesor circumscriptus Nees (Hymenoptera: Braconidae). Development time of the apple leafminer was not affected by the four apple genotypes. By contrast, the number of emerged adult moths significantly differed between the two classically bred cultivars, whereas no effect of the two transgenic apple genotypes was detected. Paralleling the observations of the apple leafminer development, no impact of the four apple genotypes on parasitoid development time and parasitism success could be detected. Although mean numbers of emerged parasitoids were lower on the cultivars with fewer emerged apple leafminers, these differences were not significant. Herbivore and parasitoid performance was not altered in the presence of pathogen inoculation. In conclusion, host plant suitability was found to be more determined by variability among classically bred apple cultivars than by the transgenic genotypes tested. To elucidate possible effects of transgenic plants within multitrophic interactions, an appropriate risk assessment incorporating the relevant controls is crucial